Normalizing furnace



G. C. KIMBALL NORMALIZING FURNAGE Filed March 2,6. 1930 VENTOR.

A TTORNEYS Patented Aug. 2, '1932 PATNT -oi-ricE y GEORGE ooox xImaALL, or IITTSBURGH, rENNsYLvANm- NORHALIZING FUBNACE Application mea Maren as, 1930. serial N. 439,164.

This invention relates broadly to furnaces for heat-treating metal products and 1 s particularly concerned with the normalizing of steel.

rllhe desired end in the normalizing of stee is the production` of a uniform or .normal sized grain throughout, and consists 1n heatin the material to a point above the -upper critical temperature, approximately 1750 or 1800 degrees Fahrenheit and then cooling slowly or rapidly to the lower critical range, approximately 1275 degrees Fahrenhelt. lt

` lis believed that the quality ofthe finished product depends a great deal on the size of the grain. For extra deep drawing material going into diierent sheet stanipings, the very line grain is considered the most desirable.

ln drawing, the sharp curves, `bends or corners of the small slzed gra-ins are comparatively smooth and, according to the opinion of some of those skilled in the art, are much less'liable to break than the uniformly large" sized grains. The Ismooth surface afforded by the fine grain material is a very desirable feature, especially when the finished article is to be covered with some thin coating such as the present day automobile finish. 1

llt has been found that the size of the grain depends upon several factors and among these v is the time involved in cooling from the upper to the lower critical temperatures. The small grain can be obtained by cooling rapidly whereas prolonged cooling will produce the larger grain sizes, other conditions being the same. 4

The present method consistsin subjecting the material during the normalizingopera-y tion to a. comparatively rapid cooling action after the upper critical point has been reachedto thereby'produce auniformly small 'sized grainand a resultant desirably smooth surface product.

An essential objeetaof the present invention, therefore, is the provision of means whereby the material passing through anormalizing' furnace may subjected to a more rapid and better regulated cooling action than `has heretofore been possible with furnaces known in the art, to thereby produce a uniformly small-sized grain and smooth surface resultant product.

Heretofore normalizing furnaces have'been designed by means of which the material passing therethrough\may be advanced at varying speeds, and it has also been proposed to remove certain sections of the furnace cover or arch structure, to thereby betterv control the rate of cooling. By the employ"- ment of such methods alone, however, the desired result herein proposed cannot be attained, and moreover," the removal of arch sections permits the furnace gases to escape at points along the furnace which may not pi'ove desirable and yet does not enable the control of temperature afforded by the present type of furnace.

In the drawing: f l v Figure l isv a view partly in side elevation and partly in longitudinal section of a. normalizing furnace'embodying the features of the present invention, broken through at vai rious points and moved togetherv to conserve \space. i Y i l, Fi 2 is a cross sectional view taken on the line 2 2, Fig. 1.

f Fig. 3 is a detail view in eleyation of a i r'oof section or bung.

Briefly, the furnace as shown is comprised in two main sections, a heating chamber generally designated at A. and a coolingV chamber in direct alignment therewith and generally designated atiB, the metal under treatment being advancedv in the direction indicated by the arrow on a succession of suitably driven conveyor disks 5,*mounte'd on transversely-disposed shaft 6, which extend through the side-walls 7 of the furnace and are. journalled on outside bearing pedestals 8. A lire-door or baille 9 is provided be.` tween the adjoining ends fof the two chambers and is adjustable vertically, to control L the passage f heat from theheating chamber of'thei Hoor of the cooling chamber overliesY a layer 11 of insulating materiali," to reduce dissipation of heat.

The roof of both chambers A and B is made in complemental abutting, removable sections a and which are superimposed up-y on'fthe side walls 7, a cushion of sand forming a seal at the point where the side walls of the sections rest upon the supporting walls 7. The roof 4sections of the heating chamber are arched and provided with a heavy lining 12 of refractory material and an outer covering 13 of heat insulating material, in order to withstand the excessively high temperatures to which this part of the furnace is-sub-v jected. The sections Z) may be provided with a relatively .light lining 12a of refractory material.

As the metal sheets or analogous stock pass from the chamber A" into the chamber B, the action of cooling from the upper critical temperature to the lower critical temperature begins and it is with this action that the present invention is concerned.

To obtain a more rapid and better regulated cooling action, an artiiicially cooled type of top wall or roof section or bung b is provided, the cooling medium being here shown as water. This form of section is shown as built up of metal plate but it will be obvious that other material could be used in place of metal and obtain the same result. Lifting lugs 14 are provided on each section, so that they may be readily moved to various points on the cooling chamber by a crane. water-cooled and thenon-water-cooled sections are duplicates in size and shape and are interchangeable, whereby many different combinations' of water-cooled and non-watervcooled sections may be provided so as to selectively bring about many diierent cooling conditions in the cooling chamber for Vthe purpose of regulating the cooling conditions in accordance with the character of the metal to be cooled. The top of each section is illustrated as of open construction, but may be closed if desired, and the roof wall 15 is arched. The lower portions of the side walls 16 .of the sections are flanged as at 17 where they rest on the side walls 7 of the furnace. The walls of each section provide a chamber or receptacle 18 which is supplied with a cooling Huid, water in the present instance, through a valved inlet pipe 19, thewater circulating in the chamber 18 due to thermal action and passing out through an outlet plpe 20. The arched wall 9 may be positioned at varying heights relativelylto the metal passing through the furnace, but it is preferred to have the said walls'in comparatively close proximity to the metal undergoing treatment, to obtain the full effect of the cooling medium.

In the example illustrated in Fig. 1, a

plurality of these artificially-cooled roof It will here be explained that the i Leeaeer sections are disposed on the end of the cooling chamber B which adjoins the heating `metal undergoing treatment through said chambers, said cooling chamber having a roof composed of interchangeable sections superimposed upon the side walls of the chamber, means forming a seal between said roof sec-l tions and the side walls of said chamber, some of said roof sections being chambered, means for supplying and circulating a cooling fluid to and through the chambered roof sections, and other of said sections being unchambered and of relatively thin construction to permit radiation of heat to the atmosphere, said roof sections capable of being interchangeably and selectively applied to said cooling chamber to regulate the rate of cooling in said chamber.

2. ln a normalizing furnace, a heating chamber, a cooling chamber disposed in communicating relation with the heating chamber, means for selectively establishing and cutting 0E communication between the chambers, andu removable and interchangeable roof sections for the cooling chamber, some of said roof sections being water cooled, whereby the positional disposition of the water cooled roof sections and the other roof sections of the cooling chamber may be selectively changed to bring about the desired cooling effect in the cooling chamber.

ln testimony whereof, l have hereunto set m hand.

y GERGE COOK KMBALL. 

